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Feb- 21, 1956 c. J. RIDGLEY 2,736,010

THERMAL ALARM DEVICES Filed July lO, 1951 3 Sheets-Sheet l dnb/wa @1m inne/vars' Feb. 21, 1956 c. J. RIDGLEY 2,736,010

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l fume/n 4me/7 msx new 2 /Yd Ti/P 7707 f/P /fYSTL 716/? 2,73 6,010 THERMAL ALARM DEVICES Cornelius J. Ridgley, deceased, late of Philadelphia, Pa., by Charlotte H. Ridgley, administratrix, Philadelphia, Pa., assigner to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application July 10, 195.1, Serial No. 235,922 2 Claims. (Cl. S40-222) This invention relates to a circuit breaker and more particularly relates to a novel combined overcurrent trip and alarm device arrangement for operating' a circuit breaker in response to overcurrent and fault conditions.

in the operation of an overcurrent trip device for circuit breakers, it has been found that the circuit breaker is often subjected to overcurrent conditions which can be rectiedv without interrupting operations by a tripping of the circuit breaker. For example, when' a total current in excess of safe condition occurs, if the operator is alerted by an' alarm which' is initiated by the occurrence of the portion of an unessential load to restore the current ow to tolerable conditions and thereby preventy interruption of service to essential units-by the opening of the circuit breaker.

in attempts to achieve this result in the past, it` has been found that the alarm provided -for the operator usually starts such a short interval ,before the breaker is tripped by the overload responsive device that it does not give the operator sufii'cient time to control the load conditions.

it has been discovered that in' the overcurrent range from t'ull current rating to overcurrent up to 250% of' normal load, it is not necessary to provideany automatic tripping operation of the breaker by the overcurrent.

Accordingly, a possible alarmv operation is provided for currents slightly in excess of the normal fully current rating up to 250% overload which informs th'eopera'tor of the existence ofl such current conditions and leaves it to his judgment to either correct the condition or to permit it to continue, as he chooses. Indeed, in many inst es under special circumstances,` the operator may r to permit the risk of damaging electrical equipment in order to maintain continuousk service. In other instances, he may, in response to the alarm, relieve'thc electrical equipment of some of its-l load and thereby prevent failure oi the electrical equipment.

From 250% to 1200% of normal current rating' the ne mal time delay trip device of the present invention `ctions together withl tripping operation occurs substantially simultaneously' with the alarm so that the operator will not have any opportunity to relieve the load. Above 1200% of normal current rating, I provide the usual instantaneous tripping operation.

in general, the above results' are achieved by preventing the tripping mechanism from performing any autocurrents above 250% to permit the usual automatic trip operation both with time delay and instantaneously.

Accordingly, an object of the invention a novel circuit breaker having 1n combination therewith operator up toy predetermined overcurrent conditions.

A further object of the invention is to provide a coml bination of an automatic tripping operation of a circuit 2,736,010 Patented Feb. 21, 1956 breaker and an alarm in which the alarm alone is effective up to a predetermined value of overload.

A further object invention is to provide an alarm indicator controlled by the current flowing in the center pole of a three-phase circuit breaker and an instantaneous trip operation by the center pole at a predetermined fault current value.

TheseI and other objects of the invention will be more fully understood from' the detailed description which is to be accompanied by the drawings, in which:

Figure 1 is a side view of one of the end poles of the circuit breaker with an overcurrent taneous above 0%.

Figure 2 isa side view of the center pole of the circuit breaker which activates the alarm system for current values' from 125% up to 1200%.

Figure 3 is a schematic circuit diagram of a three pole circuit breaker in which the outside poles have a time delay trip from 250%l to 1200% and an instantaneous trip above 1.200%, and the center pole' has an alarm and instantaneous trip; and

Figure 4 is a graph of the tripping and alarm characteristics of the overcurrent device showing the time delay action.

Referring to FigureV 4, time-current characteristic an alarm operation in combination with a tripping mechanism. Curves 1 and 2 show the characteristic of the alarm device which my novel mechanism provides. As shown, at, for example, 115% overon' the absciss'ae) the alarm will be acelapsed. For these fault current values, i. e., between continuing for 140 seconds and 25` seconds respectively, the overload trip mechanism on the outside poles' is prevented from operation, as will n A When of 250% rated load, the trip device functions to trip the circuit breaker. Curve 2 shows the characteristics of this automatic operation and is substantially identical in time delay properties to curve 1 for overloads greater than 250% and less than 12.00% of ratedcurrent'. Hence curve 2 is superimposed upon curve 1. Within these ranges and with balanced load electrical failure, that may be overloaded.

of rated load, the usual time delay automatic trip operation occurs, with an alarm device being simultaneously activated at the time the action occurs.

Referring again to curve 2, it is seen that for overloads of l200% and greater than 1200% of rated load, an instantaneous tripping operation is provided on the two outside phases. This instantaneous tripping action also occurs in the center phase at 1200% of rated load; however, the center phase has no tripping action characteristics below 1200% of normal load.

Referring now more specifically to Figure 3, the three poles 11, 12 and 13 of a circuit breaker are shown, connected between a source of power 14 and a load 15. Each pole is provided with individual trip coils 14, 15 and 16. The two outside poles 11 and 13 of the circuit breaker are identical to each other in construction and operation.

Referring to Figure l which shows the trip mechanism for one of the outside poles, the usual electromagnet core 23 is provided which in this device is U-shaped, carrying the winding 24 connected in series in the line to be protected upon its upper leg 25. The electromagnet is provided with an armature 26 pivotally mounted at 27 and biased against attraction by the energization of the magnet 23, by the Calibrating tension spring 36, one end of which is secured at 35 to the armature 26 and the other end of which is mounted on an adjustable screw 38 for varying the tension of the spring 36. The screw 33 is movable vertically by rotation. The tension of the Calibrating spring 36 is adjusted to prevent counterclockwise movement of the armature 26 for overloads less than 250% of normal load.

A latch 41 is pivotally mounted at 42 and engages the projection 43 on the armature 26.

The latch 41 is biased counterclockwise about pivot 42 by spring 44, one end of which is secured to the bimetal 48 and the other to the armature latch 41. The spring 44 will maintain latch 41 in latching engagement with armature 26 for magnetic force values corresponding to overloads below 1200% of normal load, which forces are produced by the attraction of the electromagnet 23 on the armature 26 and transmitted through the latch 41. Spring 44 hence acts to prevent clockwise rotation of the latch 41 at overloads below 1200% of rated load. At overloads greater than 1200% of normal load the force of spring 44 will be overcome by the pull of the electromagnet 23 and will allow clockwise rotation of the latch 41 to release armature 26 to move towards the pole face to engage and operate latch 44'. On operationfof the latch 44', the circuit breakers 11 and 13 are operated to their open position by their biasing springs 45.

A thermo-bi-metallic element 48 is provided with a rod 49 to which is secured a member 50 which on deection of the thermal element engages the latch 41 at 51. Element 48 is secured in any well known manner to the yoke of the magnet 23 as shown in Figure l, being secured adjacent to the turns of winding 24 and hence capable of absorbing heat dissipated by the winding 24.y Element 48 will deect to the right, referring to Figure l, when its temperature is raised by heat dissipated by the winding 24, under overload conditions, and will, through member 50, rotate the latch 41 in a clockwise direction against the action of spring 44.

The latch 41, the spring 44, the projection 50, the thermo-bi-metallic element 48 and magnet 23, comprise the latching mechanism of the outside poles of my novel tripping device, the operation of which is hereinafter described.

Armature 26 cooperates with the tripping rod 33, which actuates the latch 44 of the schematically illustrated circuit breaker 11.

The latch 41 described above in connection with Figure l, as will now be clear, locks its associated armature 26 against any attraction by the electromagnet 23 by bearing upon the projection 43 on the armature 26.

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In the event that the full current owing through the winding 24 exceeds 250% of normal current, the birnetallic element 48 associated with the outer pole will be heating by the winding 24 sufficiently to rock the latch 41 in a clockwise direction about its pivot 42 until it has been carried beyond the member 43, thus unlatching the armature 26'and permitting it to be operated by the energized electromagnet 23. Due to the arrangement described above, whereby the latch 41 engages the member 43, the comparatively small force exerted by the bimetallic element 48 on the latch 41 will be sufcient to rotate the latch 41 from engagement with the member 43.

The time required for the bimetal 48 to heat suiciently to rotate the latch 41 so that it clears the member 43 constitutes the time delay of my novel tripping mechanism. This is illustrated in Figure 4 by the combination of curves 1 and 2 representing the time it takes to release the armature 26 under various percentage overload conditions. Since the alarm circuit referred to above and hereinafter completely described, and the latch 41 are both operated by similar thermo-bi-metallic elements, the time delay curve in Figure 4 for the operation of each is identical, and hence both are represented by the combination of curves 1 and 2.

The calibrating spring 36 described above is adjusted to a tension which will prevent motion of the armature 26, due to the force exerted on it by the electromagnet 23, at overload conditions below 250% of normal load.

From the above, it will now be seen that the novel tripping device will not trip a circuit breaker at overloads below 250% but will trip a circuit breaker at overloads between 250% and l200% with a time delay for a given overload condition in accordance with curve 2 of Figure 4. To illustrate, at 500% overload the circuit breaker will be tripped open after a time delay of 18 seconds.

Instantaneous trip at overloads of 1200% normal load and above is provided by the electromagnetic action of the magnet 23 on armature Z6 which is sufficient at this current value to overcome the combined action of the springs 44 and 36. The latch 41 is rocked counterclockwise by the force applied to the armature which, on reis then attracted to the pole face of the magnet.

Hence the novel tripping scheme will provide a delayed tripping action between 250% and l200% of normal load, and in addition, will provide an instantaneous trip at overloads greater than 1200% of normal load, by virtue of the mechanism associated with the two outer phases of the three-phase system herein described.

The center phase of the three-phase system which is protected by the tripping device has an associated pole similar in some respects to the two outer poles described above. Referring to Figure 2, the numbered parts of the center pole correspond to identical parts of the outer poles with identical numbers.

The elements of the center pole which are identical in form and location to those of the outer poles are: the electromagnet core 23, the overcurrent winding 24, the armature 26, the Calibrating spring 36 and the adjustable brackets 38 and the combination for fastening the bi-metal strip 48.

The calibrating spring 36 has its tension adjusted by identical means 38 as in the case of the outer poles; however, its tension is set so that the armature 26 cannot be drawn to the electromagnet 23 until a force corresponding to an overload greater than l200% is produced by the electromagnet 23. Thus the center pole is only capable of providing an instantaneous trip for overloads greater than l200% of normal load', below 1200% of normal load no tripping action will be produced.

An alarm circuit 65--66-67--68 is provided in the center pole. This circuit is actuated by the thermo-bimetallic element 48 secured to the electromagnet 23 by means identical to that described in connection with the outside poles and whose bending action is identical to that described in connection with the outside poles. An extension 63 is secured to the bi-metal extension arm 49 and insulated therefrom by au insulating block 64.

Extension 63 operates a contact 65 secured to the snap element 66 of a microswitch 69. These two contacts 65 and 66 are connected to the alarm indicator 67 and a suitable direct current source 68.

The engagement of the contacts 65 and 66 will occur for an overload greater than 115%, in accordance with curve 1 of Figure 4. Thus the alarm 67 will ring after a pre-set time delay. This alarm will operate alone at overloads from 115% to 250%. At overloads from 250% to 1200% the alarm will operate simultaneously with the opening of the latches of the outer poles with time delay, as mentioned above, since bi-metals 48 of Figures 1 and 2 are of identical material. Above 1200% overload, the alarm 67 and the instantaneous trip will operate simultaneously.

In the foregoing the invention is described solely in connection with specic illustrative embodiments thereof. Since many variations and modifications of the invention will now be obvious to those skilled in the art, it is preferred that the invention is bound not by the specic disclosures herein contained but only by the appended claims.

What is claimed is:

1. In a multipole circuit breaker for protecting an electric circuit comprising a time delay device an instantaneous trip device and a signal device; said instantaneous trip comprising an electromagnet responsive to fault currents above 1200%, an armature for said electromagnet, and a latch engaging said armature and normally preventing operation of said armature by said electromagnet for fault currents below a predetermined amplitude; said time delay device operating said latch out oi engagement with said armature to permit operation of its associated armature by said electro-magnet in response to said predetermined fault currents between 250% and l200% of normal load current, said signal device and said time delay device comprising a bimetallic element, a lirst and second Contact, a source oi power and an indicating means, said indicating means being energized by said power source when said irst and second contacts are in the engaged position; said iirst contact being attached to said bimetallic element and constructed to be movable into engagement with said second contact responsive to movement of said bimetallic element to thereby allow energization of said indicating means by said power source when the magnitude of current is between 115% and 250% of the normal load current.

2. In a multi-pole circuit breaker for protecting an electrical mechanism, an electromagnet for each pole responsive to fault currents in said circuit for controlling the opening of said circuit breaker, each of said electromagnets having a latched armature; said electromagnets on at least two of said poles being responsive to short circuit currents for operating this associated armature to trip their associated poles of said circuit breaker; time delay means connected to said armature of said two electromagnets for delaying operation of said armatures for predetermined intervals of time when the fault currents flowing in said electromagnets are of the overload range, a signal control device operated by the electromagnet of one of said poles when the fault currents are overload currents below a first predetermined value, said signal control device operatively connected to eifect energization of a signaling unit independent of said latched armature, said electromagnet elective to disengage said latch for instantaneous trip when the fault current is above a second predetermined value, said time delay means etfective to cause disengagement of said latch when the fault current is in the range between said first and second predetermined value said time delay means and said signal control device comprising a bimetallic element operable by the heat of said electromagnet, said bimetallic element being operatively connectable to said latched armature to cause disengagement thereof responsive to fault current between said first and second predetermined value and said bimetallic element being further constructed to carry the movable contact ol a pair of cooperable contacts, said cooperabie contacts comprising a portion of said signaling circuit whereby engagement of said Contact allows energization of said signalling unit, said movable contact being moved into contact engaged position when said bimetallic member is moved responsive to overload current below said irst predetermined value.

References Cited in the tile of this patent UNITED STATES PATENTS 

